PREHEAT oven to 425 degrees.
SLICE the sweet potatoes in half lengthwise, and then slice them into 1/2-inch-thick slices.
LINE a rimmed sheet pan with foil or parchment paper.
PLACE sliced sweet potatoes and green beans on the pan.
TOSS with 2 Tablespoons olive oil and 1/4 teaspoon kosher salt and black pepper to taste.
ROAST for 20 minutes, stirring once halfway through roasting
While vegetables roast, make the vinaigrette
In a small bowl, COMBINE remaining 2 Tablespoons of olive oil, balsamic vinegar, mustard, garlic and ¼ teaspoon of salt.
REMOVE vegetables from oven.
STIR in cranberries and thyme..
RETURN pan to oven.
ROAST an additional 5 minutes.
TOSS vegetables with the vinaigrette. SERVE vegetables warm or at room temperature.